EXCHANGE 


Geology  of  Sangamori  County 


BY 


s-. 


A.  R.  CROOK,  Ph.  D. 

Curator  Illinois  State  Museum  of  Natural  History 


1912 


f .. 

K- 


SPRINGFIELD,  ILL. 
ILLINOIS  STATH  JOURNAL  Co.,  STAT«  PRINTWMI 


Geology  of  Sangamon  County 


BY 


A.  R.  CROOK,  Ph.  D. 

Curator  Illinois  State  Museum  of  Natural  History 


1912 


SPRINGFIELD,  ILL. 

ILLINOIS  STATB  JOURNAL  Co.,  STATB  PRINTER* 
1912 


ILLUSTRATIONS. 


PAGK. 

Fig.  1 — Governor  Deneen  inspecting  Divernon  Coal  Mine  April  20,  1910 1 

Fig.  2  — Picking  pebbles  in  Illinoian  till  by  an  old  mill  on  Sugar  Creek 7 

Fig.  3— A  mass  of  fossil  corals  (Syringopora  multattenuata)  found  near  Springfield,  now  in  State 

Museum 

Fig.  4 — Fossil  corals  (Lophophi/Uum  proliferum)  found  near  Springfield,  now  in  Museum 

Fig.  5 — Fossil  brachiopods  (Spirifer  multiyranosa)  found  near  Springfield,  now  in  Museum 

Fig.  G — dossil  lamillibranchs  (Leda)  found  near  Springfield,  now  in  Museum 

Fig.  7 — Fossil  gastropods.    At  the  left  Pleurotomaria  ?pliaerulata,  next  Bellerophon  percarinatus. 

All  from  Roll's  Ford,  now  in  State  Museum 14 

Fig.  8— Fossil  gastropods  (Subulities  peracuta  and  Subulites  inornatus')  found  at  Roll's  Ford,  now 

in  Museum 14 

Fig.  9— Outcrop  of  the  limestone  (No.  8  in  typical  section)  which  furnished  the  stone  for  the  Old 

State  House,  Springfield.    Quarry  quarter  mile  west  of  Crow's  Mill 16 

Fig.  10— Old  Crow's  Mill  quarry  now  grass  grown . 17 

Fig.  1 1—  Map  of  Sangamon  County  showing  location  of  coal  mines,  clay  pits,  quarries 19 

Fig.  12- Sangamon  County  is  a  prairie  save  where  streams  have  fashioned  valleys  or  glaciers  de- 
posited their  burdens 


GEOLOGY  OF  SANGAMON  COUNTY. 


a 

i  -teat 


GENERAL    GEOLOGY. 

Every  citizen  of  Sangmon  county,  young  or  old.,  illiterate  or  learned, 
unoccupied  or  engaged  in  agriculture.,  in  mining,  in  commerce  or  the 
learned  professions,  is  at  one  time  or  another,  in  one  way  or  another, 

interested  in  or  affected  by  the 
geological  history  of  Sangamon 
county.  The  boys  and  girls  and 
the  men  and  women  of  the  county 
would  do  well  to  study  its  geol- 
ogy, to  consider  its  fields,  and  to 
examine  its  mines  as  does  even 
the  Governor  of  the  State,  as  may 
l)e  seen  from  this  snap  shot,  which 
the  writer  took  two  years  ago  at 
Divernon  (Fig.  1). 

The  following  account  is  in  the 
main  a  reprint  of  an  article  which 
I  wrote  for  the  Historical  Ency- 
clopedia of  Illinois,  Vol.  II,  pages 
814-822. 

As  among  the  races  of  men  the 
iniquities  of  the  fathers — and 
their  good  deeds,  too — are  often 
visited  upon  their  children,  so  in 
the  rock  world,  present  condi- 
tions are  closely  related  to  past 
events.  In  inorganic  as  well  as 
organic,  in  inanimate  as  well  as 
animate  nature,  today  depends 
upon  yesterday  and  the  morrow 
upon  today.  Sangamon  county 
is  now  the  home  of  a  large  num- 
ber of  prosperous  people  because 
of  a  series  of  events  which  have  been  transpiring  during  past  millenniums. 
If  those  occurrences  had  been  different  the  black  soil  and  blacker  coal  of 
the  county  would  have  been  wanting  and  in  their  place  there  might  have 
been  volcanic  mountains  or  a  deep  ocean.  Leonardo  da  Vinci,  poet,  artist 
and  man  of  science,  had  difficulty  in  convincing  his  people  that  the  ocean 

—2 


FIG.   1 — Governor  Deneen   inspecting 
Divernon  coal  mine,  April  20,   1910. 


6  'V.  GSQLQGY' OF  SANGAMON  COUNTY 

at  one  time  covered  Italy.  When  fossil  fish  were  found  in  rocks  far  up 
on  the  Apennines,  the  finders  decided  that  the  Creator  had  been  trying 
his  hand  at  making  fish  and  had  discarded  such  as  were  imperfect.  A 
fossil  was  considered  a  reject,  a  lusus  naturae.  Here,  in  Illinois,  on  a 
summer  day,  the  average  citizen  can  with  difficulty  be  brought  to  realize 
that  the  cool  sea  breezes,  now  a  thousand  miles  away,  once  played  over 
all  of  Sangamon  county  and  the  whole  state.  But  that  such  is  the  fact 
is  evident,  since  all  of  the  rocks  of  this  region  were  made  under  water 
and  most  of  them  under  salt  water.  The  top  layers,  the  last  to  be  made, 
were  worked  over,  carved,  denuded,  transported,  and  redeposited  by  wind 
and  by  rivers  of  water  and  of  ice.  All  of  these  rocks — those  deeply 
buried  and  those  on  the  surface — are  silent  Avitnesses  of  past  conditions, 
of  mighty  forces,  of  changing  climates.  To  understand  them  the  investi- 
gator must  look  in  many  directions.  He  must  literally  delve  deeply  and 
must  leave  no  stone  unturned.  Fortunately,  both  nature  and  man  have 
done  much  to  help  him  in  his  investigation.  Where  streams  have  carved 
out  valleys,  various  layers  of  soil  and  rock  have  been  exposed.  In  places, 
shafts  have  been  sunk  several  hundred  feet  in  search  of  coal,  and  here 
and  there  drill  holes  have  been  put  down  to  even  a  greater  depth.  From 
these  various  cuttings  knowledge  has  been  obtained  of  the  underlying 
rocks.  Similar  procedure  in  other  parts  of  the  State  has  added  still 
further  information,  so  that  a  good  idea  of  the  underlying  strata  can  now 
be  obtained.  Although  the  anatomy  of  the  earth  is  not  disclosed  here, 
as  it  is  in  mountain  regions  where  strata  are  tilted  and  laid  bare,  yet 
much  is  known  of  the  rocks  which  underlie  the  region. 

CHARACTER  OF  THE  UNDERLYING  BOCK. 

Beginning  at  the  top  and  proceeding  downward,  the  following  layers 
are  encountered : 

First — There  is  a  layer  of  soil  which  is  worked  over  by  man  and 
penetrated  by  plant  roots,  and  which  is  about  one  foot  thick.  Below  it 
are  two  or  three  feet  of  buff  clay,  which  is  penetrated  in  digging  cellars 
for  houses  and  which,  when  spread  out  over  back  yards,  causes  would- 
be  gardeners  much  annoyance,  since  it  is  sticky  when  wet  and  very  hard 
when  dry.  It  is  followed  by  several  feet  of  a  mixture  of  clay,  lime  and 
fine  sand,  in  places  rich  in  organic  materials.  This  earth  is  called  loess. 
It  had  been  borne  by  wind  and  water  from  some  distant  place  and  spread 
out  over  the  country,  and  later  was  buried  by  the  overlying  deposits. 
The  particles  which  compose  it  are  quite  uniform  in  size,  as  would  be 
expected  of  wind  borne  material,  or  earth  that  had  been  deposited  in 
quiet  lakes.  Even  in  recent  years  the  people  of  this  and  neighboring 
states  have  seen  dust  carried  by  high  winds,  darkening  the  sun  and 
drifting  like  black  snow  on  lawns  and  porches.  Loess  was  formed  in 
some  such  manner  and  consequently  exhibits  slight  stratification,  but 
parts  vertically,  so  that  ravines  cut  through  it  retain  for  a  long  time 
vertical  walls,  as  can  well  be  seen  in  the  "Zoo  Park,'7  four  miles  north 
of  Springfield. 


GEOLOGY    OF    SANGAMOX    COUNTY  7 

The  loess  is  underlain  by  a  sandy  layer,  at  times  as  much  as  ten  feet 
in  thickness.  This  indicates  that  lakes  or  rivers  sorted  the  material,  as 
they  are  now  doing  around  Lake  Michigan  and  along  Fox  river.  Below 
the  sandy  layer  is  a  twenty-foot  bed  of  blue  gravelly  clay,  rather  tough 
to  dig  through,  and  hence  called  hardpan.  Its  geological  name  is  Illi- 
noian  till.  (Fig.  2.)  During  the  ice  age  glaciers  bore  from  Canada 
and  the  intervening  country  gravel  and  clay,  and,  upon  melting,  depos- 
ited these  materials  sometimes  in  ridges  and  mounds,  at  other  times  as 
mud  flats  in  shallow  lakes.  The  "Illinoian  till"  consists  of  such  mate- 


FIG.   2 — Picking-  pebbles  in  Illinoian  till  by  an  old  mill  on  Sugar  creek. 

rial.  Below  it  comes  a  layer  of  sand  or  muck,  that  in  places  attains  a 
thickness  of  five  feet  and  constitutes  the  so-called  Yarmouth  zone. 
Immediately  underneath  it,  another  bed  of  glacial  material  much  older 
than  the  Illinoian  till,  and,  from  the  fact  that  it  is  widely  spread  over 
Kansas,  called  the  Kansan  till,  is  encountered.  It  is  from  twenty  to 
thirty  feet  thick. 

After  penetrating  these  superficial  deposits  of  soil,  loess,  sand,  and 
till  of  two  groups,  the  top  rock  of  the  county  is  reached.  In  many 
places,  as,  for  example,  along  Spring  and  Sugar  Creeks  and  in  the 
valley  of  the  Sangamon,  these  bed-rocks  have  been  exposed  by  the  cut- 
ting away  of  the  overlying  material,  and,  as  is  universally  the  case  in 
prairie  states,  the  best  idea  of  the  rock  constituents  of  the  region  are  to 
be  obtained  along  the  beds  of  the  streams.  Since  the  strata  dip  gently 
(about  six  feet  per  mile)  towards  the  east  and  south,  the  lowest  beds  in 
the  county  are  exposed  on  Richland  creek  and  the  Sangamon  river  in 
Salisbury  township.  All  of  the  strata  are  composed  of  three  kinds  of 
rocks  only,  namely :  shale,  sandstone  and  limestone — though  they  vary 


~8  GEOLOGY   OF   SANGAMON    COUNTY 

in  purity  as  they  graduate  into  each  other,  the  shales  changing  to  sand- 
stone when  the  amount  of  sand  increases,  or  into  limestone  when  the 
amount  of  calcium  carbonate  becomes  greater  in  quantity.  The  presence 
of  iron  or  carbon  changes  the  appearance  of  the  rocks. 

Beginning  near  the  source  of  Sugar  creek  in  the  southern  part  of  the 
county  and  proceeding  down  stream,  a  succession  of  sixty  feet  of  strata 
may  be  noticed.  They  are :  First,  layers  of  sandy  shale  and  sandstone 
twenty  feet  thick;  next,  brecciated  limestone  twelve  feet  thick;  black 
shale,  three  feet  thick;  soft  clay  shale,  six  feet  thick;  calcareous  sand- 
stone, five  feet  thick;  bituminous  shale,  six  feet;  and  Carlinville  lime- 
stone, eight  feet  thick.  Below  the  Carlinville  limestone  is  a  thick  bed 
of  sandy  shale,  which  is  underlain  by  a  three-foot  bed  of  clayey  lime- 
stone rich  in  fossils;  and  a  thin  bed  of  bituminous  shale.  Immediately 
under  it  is  a  two-foot  thick  bed  of  coal  called  Coal  No.  8,  which  out- 
crops at  Eiverton.  In  early  days,  before  the  thick  deposits  which  are 
now  used,  were  discovered,  it  was  dug  out  along  the  banks  of  the  river 
at  that  place,  then  called  Howletts,  and  on  Spring  creek  northwest  of 
Springfield.  Today  it  is  not  used. 

Below  Coal  No.  8  is  a  layer  of  fine  clay  (three  feet  thick)  an  impure 
limestone  (six  feet  thick)  and  forty  feet  of  soft  shaly  sandstone.  Thus 
a  typical  section  of  the  top  two  hundred  or  more  feet  of  the  rocks  of 
Sangamon  county  would  be  as  follows : 

Strata.  Feet. 

1.  Soil    1 

2.  Loess,  often  clayey 5  to  15 

3.  Sand 3 

4.  Illinoian  till   (clay,  "hardpan")  . 11  to  20 

5.  Yarmouth  zone  (Sand,  muck) 5 

6.  Kansan  till   20  to  30 

7.  Shales  and  sandstone   .  .  . 20 

8.  Limestone   (brecciated)    12 

9.  Shales,  black,  slaty    3 

10.  Shales,  clayey   6 

11.  Sandstone,  calcareous  and  ferruginous 5 

12.  Shales,  bituminous 6 

13.  Limestone,  "Carlinville"   8 

14.  Shale,  sandy   40 

15.  Limestone,  clayey,  rich  in  fossils 3 

16.  Shale,  bituminous    1 

17.  Coal  No.  8 2 

18.  Clay,  fine  3 

19.  Limestone,  impure   6 

20.  Sandstones,  soft,  shaly 40 

Layers  No.  1  to  No.  13,  are  exposed  on  Sugar  creek.  Nos.  14  and  15, 
which  outcrop  in  a  ravine  west  of  the  place  where  the  old  Springfield 
to  Peoria  road  crosses  the  Sangamon,  are  full  of  fossils,  more  than  sixty 
species  having  been  found  and  described. 


GEOLOGY    OF    SANGAMON    COUNTY 

An  excellent  idea  of  six  hundred  feet  of  strata  underlying  Divernon, 
Sangamon  county,  can  be  obtained  from  drill  cores  which  have  recently 
been  received  at  the  State  Museum.  In  early  times,  when  miners  were 
desirous  of  knowing  what  was  beneath  the  surface,  it  was  necessary  for 
them  to  laboriously  dig  a  shaft.  Such  work  required  many  months  of 
hard  labor.  Today,  one  wishing  to  have  an  idea  of  underlying  strata 
needs  but  to  drill  a  hole  by  means  of  one  of  the  many  excellent  drills 
which  are  available.  A  diamond  drill  can  rapidly  penetrate  to  great  depth 
at  a  cost  of  but  two  or  three  dollars  per  foot.  The  drill  consists  of  an 
iron  pipe,  in  the  end  of  which  rough  diamonds  are  fastened  both  on 
the  outer  and  inner  edge.  The  pipe  is  rapidly  rotated  and  the  core  which 
•comes  up  on  the  inside  of  the  pipe  can  be  drawn  out  and  is  an  excellent 
record  of  the  strata  penetrated.  Water  is  used  to  keep  the  hole  free  from 
dirt.  Naturally  very  soft  formations,  such  as  those  of  a  clayey  or  sandy 
nature,  are  washed  away  and  their  record  is  lost.  The  core  of  this 
Divernon  coal  mine  is  two  inches  in  diameter.  A  careful  record  of  the 
boring  was  kept  by  Mr.  Theodore  Wilde.  Since  much  of  the  material 
penetrated  was  soft  shale  or  clay  easily  soluble,  it  was  washed  away  and 
the  present  core  is  but  three  hundred  and  seventy  feet  long.  The  rocks 
penetrated  are  alternating  limestone,  shale,  coal  and  sandstone.  It  is  a 
surprising  fact  that  the  total  amount  of  limestone  was  hut  twenty-two 
feet  of  pure  limestone  and  but  thirty-six  feet  more  of  impure  limestone, 
•a  total  of  fifty-eight  feet.  The  total  sandstones  amounted  to  one  hun- 
dred and  three  feet.  The  shales  make  up  the  mass  of  the  underlying 
rock,  there  being  three  hundred  and  seventy-four  feet  of  pure  shale,  or 
four  hundred  ten  feet  of  more  or  less  shaly  material  of  various  kinds — 
blue,  black,  green,  mottled;  fairly  hard  or  soft;  calcareous,  arenaceous, 
micaceous,  bituminous.  The  shales  are  all  soft  in  comparison  to  other 
rocks  and  rather  easily  soluble  as  they  represent  the  mud  of  the  ocean. 
When  stuck  in  the  mud  on  one  of  our  country  roads,  the  traveler  may 
solace  himself  with  the  thought  that  there  is  more  potential  mud  below 
him — two-thirds  of  all  the  rock  for  six  hundred  feet  beneath  being  ready 
to  furnish  more  mud  as  required !  Our  farms  need  never  be  exhausted, 
if  we  can  but  wash  off  the  surface !  Twenty-five  feet  of  the  six  hun- 
dred consists  of  coal,  a  larger  total  than  that  of  good  limestone !  The 
coal  varies  from  beds  two  inches  in  thickness  to  one  seven  feet  eleven 
inches  in  thickness. 

GEOLOGICAL  FORMATIONS. 

All  of  the  strata  given  in  the  above  typical  section  are  found  in  the 
Upper  Productive  division  of  the  Pennsylvanian  formation — a  formation 
which  closes  the  period  commonly  called  the  Carboniferous  period— 
since  at  that  time  all  the  great  coal  deposits  were  formed.  The  forma- 
tion is  called  Pennsylvanian  since  it  is  so  well  developed  in  Pennsylvania. 
The  Lower  Productive  is  the  division  of  the  Pennsylvanian  most  coveted 
by  mankind  because  it  is  the  coal  division,  par  excellence.  In  Pennsyl- 
vania the  subdivisions  of  the  Pennsylvanian,  beginning  with  the  bottom, 
are  as  follows:  1,  Pottsville  sandstone  or  Millstone  grit;  2,  Alleghany 


10  GEOLOGY   OF    SAXGAMON    COUNTY 

series;  3,  Conemaugh;  4,  Monongahela.  The  divisions  in  Illinois  are: 
1,  Mansfield  sandstone;  2,  Carbondale  shale  and  limestone;  3,  McLeans- 
boro  limestone,  shale  and  sandstone.  The  Carlinville  limestone  of 
Illinois,  No.  13  in  the  above  section,  possibly  corresponds  with  the  Cone- 
maugh, being  in  the  Upper  Productive.  The  chief  coal  beds  of  Sanga- 
mon  county,  Nos.  5  and  6,  occur  in  the  Carbondale  series,  that  is  to  say 
in  the  top  division  of  the  Lower  Productive  (strata  which  may  be  cor- 
related with  the  Upper  Freeport  and  Kittaning,  which  are  parts  of  the 
Alleghany  series  in  the  Lower  Productive  formation).  In  Sangamon 
count}7  the  McLeansboro  attains  a  thickness  of  about  two  hundred  feet 
and  the  Carbondale  a  thickness  of  about  three  hundred  feet.  Below  the 
latter  formation  is  a  one  hundred  fifty  foot  thick  bed  of  Mansfield 
(Pottsville)  sandstone,  finer  grained  and  lacking  the  coarse  gravel  which 
characterizes  this  formation  in  Pennsylvania.  It  was  deposited  millions 
of  years  ago  on  the  upturned  and  eroded  strata  of  the  rocks  which 
constitute  the  Mississippian  system,  so-called  since  so  well  developed 
along  the  Mississippi  river.  It  consists  in  descending  order  of  the 
following1  members: 

The  Chester  (Birdsville,  Tribune,  Cypress)  standstones,  600  feet;  St. 
Genevieve  limestone,  200  feet ;  St.  Louis  limestone,  200  feet ;  Salem  lime- 
stone, 100  feet;  Warsaw  shales,  40  feet;  Keokuk  limestone,  100  feet; 
Burlington  limestone,  200  feet;  Kinderhook  sandstone,  200  feet.  The 
total  thickness  of  these  strata  in  Sangamon  county  however,  is  less  than 
six  hundred  feet. 

Proceeding  downward  layers  of  shale  and  limestone,  200  feet  thick, 
are  encountered.  Their  fossils  and  physical  character  indicate  that  they 
are  a  part  of  the  Devonian  system.  A  diamond  drill  core  sunk  to  a 
depth  of  1,500  feet  at  Springfield,  shows,  according  to  Savage2  that  the 
Devonian  black  shale  begins  at  a  depth  of  1,339  feet.  Below  the  De- 
vonian the  Silurian  is  represented  by  possibly  one  hundred  feet  of 
Niagara  limestone.  Judging  from  strata  in  other  parts  of  the  State, 
which  dip  under  the  above  enumerated  formations,  various  divisions  of 
the  Ordovician  and  Cambrian  formations  would  be  penetrated  in  a  further 
descent;  and  it  would  be  noted  that  one  hundred  feet  of  Cincinnati  sand- 
stone and  shale,  three  hundred  feet  of  Trenton-Galena  dolomite  and  one 
hundred  feet  of  St.  Peters  sandstone,  underlie  the  formations  previously 
encountered  in  deep  drilling.  Though  positive  data  are  wanting,  it  is 
more  than  likely  that  the  Magnesian  limestone  is,  in  this  region,  under- 
lain by  Potsdam  sandstone,  since  borings  in  the  northern  part  of  the 
State  have  shown  these  formations  to  be  1,000  feet  in  thickness,  and  to 
be  sloping  under  the  above  enumerated  strata. 

These  relationships  can  best  be  seen  in  the  generalized  geologist  section 
given  on  page  opposite. 

1  E.  F.  Lines,  Ills.  State  Geological  Survey.    Bull.  No.  17,  p.  60. 

2  Copy  of  log  discussed  by  T.  E.  Savage,  now  in  possession  of  J.  A.  Udden,  Augustana  College,  Rock 


GEOLOGY  OF  SANGAMON  COUNTY 
GENERALIZED  GEOLOGICAL  SECTION. 


11 


Systems. 

Series. 

Rocks. 

Thickess  . 

Recent  or  Human 

Surface  soils 

1  foot 

f  Loess  

8  feet.  . 

Pleistocene  or  Glacial 

{  Illinoian  till 

15  feet 

[  Kansan  till  

16  feet.. 

>  1 

Q}  "o 

£<  3  I  McLeansboro 

Shales,  limestones,  (coal  un~ 

important)  

200  feet  

Pennsylvanian  

P  £ 

PH 

®  1 

{3:3     Carbondale 

Coals  numbers   2  to  6  lime- 

£§ I 
^-d    Mansfield  (Potsville) 

stone,  shale,  sandstone  
Massive  sandstone 

300  feet... 
150  feet 

1 

£ 
Chester  

St.  Genevieve  
St.  Louis  

Limestone 

120  feet 

Mississippian    . 

Salem 

Limestone 

100  feet 

Keokuk  (Warsaw)  

Shale  and  limestone 

200  feet 

Burlington 

Limestone 

100  feet 

[ 

Kinderhook  

Limestone,  shale  .  .  . 

160  feet 

Devonian  

Shale  and  limestone 

200  feet 

Silurian.  . 

Niagara 

Limestone 

100  feet 

Trenton-Galena  

Dolomite  

Ordovician  < 

St.  Peter 

Sandstone 

Lower  Magnesian  

Limestone  

Cambrian  

Potsdam 

Sandstone 

Older  rocks  than  the  Potsdam  are  not  found  in  the  State  of  Illinois. 
Noticeable  is  the  absence  of  the  newer  rocks  which  are  found  in  many 
parts  of  the  world.  After  the  Pennsylvanian  period  long  eras  passed 
during  which  the  rocks  of  succeeding  periods  were  formed.  Named  in 
order  beginning  with  the  oldest  they  are :  the  Permian,  Triassic,  Jurassic, 
Comanchean,  Cretaceous,  Eocetne,  Miocene  and  Pliocene.  The  con- 
structive agencies  which  recorded  the  passing  of  the  millenniums  in- 
volved in  those  periods,  were  as  active  and  extended  as  the  agencies  whose 
work  has  been  recorded  in  the  rock  strata  underlying  the  prairies  of  San- 
gamon  county. 

ORIGIN  OF  THE  BOCKS. 

None  of  the  rocks  in  Sangamon  county  were  formed  by  fire  as  were 
many  rocks  in  mountain  regions.  Either  wind  or  water  were  the  agents 
active  in  their  construction.  The  water  in  which  they  were  deposited 
was  cold,  sometimes  salty,  other  times  fresh.  Sometimes  it  flowed  in  a 
river  of  water  or  of  ice.  At  other  times  it  constituted  a  lake  or  an  ocean. 
The  kind  of  rock  and  the  fossil  remains  contained  therein  lead  to  such  a 
conclusion.  Sandstone,  shale  and  limestone  are  the  only  kind  of  rocks 
native  to  the  county.  The  sandstones  were  formed  along  shores  of  great 
lakes  or  oceans,  as  they  are  being  formed  today  when  waves  and  winds 
carry  away  soluble  or  light  material  from  the  debris  of  the  coast,  leaving 
the  heavier  and  insoluble  substances,  usually  particles  of  quartz,  sorted 
according  to  size.  Farther  from  the  shore  line  were  formed  clay  deposits 
and  shales  which  are  composed  of  finer  materials  than  is  sandstone,  ma- 
terials which,  because  of  their  fine  subdivision,  would  be  held  longer  in 


12 


GEOLOGY    OF    SAXGAMOX    COUNTY 


suspension  and  transported  farther  into  the  region  of  deep  water.  Shales 
indicate  that  the  shore  line  was  sinking  when  they  were  deposited  upon 
sand.  Farther  still  from  the  shore,  water  would  he  reached  which  was 
nearly  free  from  mechanically  suspended  sediments,  but  which  contained 
abundance  of  dissolved  salts,  chief  of  which  was  calcium  carbonate. 
Myriads  of  protozoa  (rhizopods),  coelenterata  (sponges,  corals),  echino- 
dermata  (crinoids,  asteroids,  echinoids),  mollusca  (bryozoans,  brachio- 
pods,  lamellibranchs,  gasteropods  and  cephalopoda),  and  vertebrata,  ex- 
tracting the  calcium  carbonate  and  other  salts  from  the  waters,  trans- 
formed them  into  shell  substances  or  bones.  Upon  the  death  of  the 
animals  these  shells  and  bones  fell  like  gentle  rain  upon  the  floor  of  the 
ocean,  forming  extensive  deposits  of  calcareous  material,  which  are  the 
chief  constituents  of  limestone.  The  floor  of  the  ocean  rising  again,  the 
order  was  reversed,  shale  being  deposited,  then  sandstones  and  gravel. 
Finally  the  ocean  receding  entirely,  all  the  region  projected  above  the 
water  level.  Thus  the  succession  of  rocks  indicates  the  ebb  and  flow  of 
the  water,  the  viscissitudes  of  the  periods  during  which  the  various  strata 
were  being  put  down. 

SOME  CHARACTERISTIC  FOSSILS. 

In  addition  to  the  testimony  of  the  rocks  themselves  is  that  of  the 
remains  of  the  animals  which,  at  one  time,  lived  in  the  ocean  that  covered 
this  region,  died,  were  buried  in  the  mud.  changed  to  stone  and  thus  con- 


FIG.   3 — A  seven-inch   mass   of  fossil   corals    (Syringopora)    found   near   Springfield, 

now  in  the  museum. 


GEOLOGY    OF    SANGAMON    COUNTY 


13 


tributed  to  the  formation  of  those  rocks.  The 
accompanying  photographs  show  fossils  now  in 
the  State  Museum,  which  were  found  at  Koll's 
ford  on  the  Sangamon  river.,  about  six  miles  north- 
west of  Springfield.,  and  others  found  on  Sugar 
creek  a  few  miles  south  of  the  city.  More  than 
seventy-five  different  species  of  fossils  have  been 
found  in  the  county,  but  the  few  illustrations 
here  presented  are  sufficient  to  give  an  idea  of 
life  of  those  remote  periods  and  to  show  how 
events,  which  occurred  millions  of  years  ago,  are 

recorded  in  the  rock 
pages  of  geological 
history,  a  history 
which  deals  with  such 
unlimited  periods  of 
time  as  to  dwarf  into 
insignificance  the  few 
years  within  w  h  i  c  h 
man  has  left  his  rec- 
ords on  the  earth. 

The  picture  (Fig. 
3)  is  that  of  a  seven- 
inch  mass  of  coral 


FIG.  4 — Fossil  corals 
found  near  Spring- 
field, now  in  mu- 
seum. 


.(  Syringopora    multat- 

tenuata  )  ,  a  coral  which 

lived  in  communities. 

The   individuals   were 

cylindrical  cor  alii  tes 

connected   by   hollow 

processes    or   by   hori- 

zontal expansions.  The 

walls   were   thick   and 

wrinkled  and  the  inner 

part  of  the  calcareous 

tube    was    divided    by 

delicate  ridges  formed  by  faint  septa.     This  coral 

was  most  luxuriant  in  carboniferous  times. 

Another  coral  is  shown  in  Fig.  4.  These  corals 
were  single  individuals,  cone-shaped  and  about 
as  long  as  the  joint  of  the  little  finger  of  a  man's 
hand.  They  suggest  a  "horn  of  plenty."  The 
skeleton  of  this  coral  (Lophophyllum  proliferum) 
is  ribbed  on  the  outside  so  as  to  show  the  meeting 

of  the  hundred  or  more  partitions  or  septa  which    FJG   g  _  Fossil  lameiii- 
project  out  into  the  body  cavity.     As  in  the  case 
of  all  corals,  the  calcareous  portions  were  covered 


FIG.  5 — Fossil  brach- 
iopods  found  near 
Springfield,  now  in 
museum. 


branchs  found  near 
n°W   : 


GEOLOGY    OF    SAXGAMOX    COUNTY 


by  jelly-like  masses.  Corals  are 
all  exclusively  marine  and  indi- 
cate that  the  water  covering  the 
country  at  that  time  was  a  part 
of  the  ocean. 

Brachiopods  thrived  in  abun- 
dance in  those  waters.  From 
many  species  the  one  shown  in 
Fig.  5  (Spirifer  multigranosa) 
illustrates  the  shape  of  the  shells. 
Brachiopods  were  so  named  since 
their  arms  are  used  as  feet.  An 
interesting  part  of  their  anatomy 
are  the  spirally  coiled  ribbons 
which  support  fleshy  cartilagin- 
ous arms  fringed  with  movable 
cirri  or  tentacles  which  set  up 
currents  in  order  to  bring  food  to 
the  mouth. 

In  Fig.  6  are  shown  mollusks 
in  the  group  of  Lamellibran- 
chiata,  animals  with  laminated 
gills.  The  shells  of  this  mollusk 
(Leda),  formerly  called  Yolida) 


FIG.    8 — Fossil    gastropds   found   near 
Springfield,  now  in  museum. 


FIG.  7 — Fossil  gastropods  (left,  Pleur- 
otomeria  ;  right,  Bellerophon)  found 
near  Springfield,  now  in  museum. 


had  compact,  thin  walls  closed 
with  teeth  in  two  series  meeting 
below  the  umbones,  and  resemble 
in  a  marked  manner,  the  modern 
clam  in  many  respects. 

Gastropods,  animals  w  h  i  c  h 
walked  on  their  stomachs  just  as 
do  snails,  are  represented  in  Fig. 
7.  In  the  left  hand  column  is 
Pleurotomaria  sphaerulata,  a  gas- 
tropod having  a  spiral  of  medium 
height,  conic  section  and  sub- 
spherical  outline.  Several  hun- 
dred species  of  these  gastropods 
are  known.  Another  genus,  Bell- 
erophon percarinatus,  is  shown 
in  the  next  column  of  the  same 
figure.  It  is  an  interesting  ani- 
mal with  its  shell  bilaterally 
symmetrical  and  coiled  in  one 
plane.  The  broad  aperture,  oval 
in  shape,  and  with  flaring  outer 
lip,  produces  a  striking  shape. 


GEOLOGY    OF   SANGAMON    COUNTY  15 

It  was  named  Bellerophan  after  a  Greek  mythological  hero.  More  than 
three  hundred  species  have  been  found  in  the  palaeozoic  era  and  the  max- 
imum of  development  was  reached  in  the  carboniferous  period. 

The  Pyramidellidae,  another  family  of  gastropods,  all  of  which  were 
marine  animals,  are  represented  by  several  representatives  of  the  genus 
Subulites  (Polyphemopsis).  The  species  peracuta  (so-called  because  in 
form  they  are  very  sharp)  and  inornatus  (not  ornamented)  are  repre- 
sented in  Fig.  8.  They  are  turreted  shells  with  oval  aperture  and  sharp 
outer  lip. 

In  the  State  Museum  there  are  more  than  thirty  different  species  of 
fossils  similar  to  those  shown  in  these  two  photographs,  and  they  give 
clear  ideas  of  the  relation  of  the  rocks  of  Sangamon  county  to  those  of 
similar  age  in  other  parts  of  the  world. 


16 


GEOLOGY    OF    SANGAMON    COUNTY 


ECOXOMIC  DEPOSITS  OF  THE  COUNTY. 

BUILDING  MATERIALS. 

Sand  deposits  do  not  exist  in  any  quantity.  Such  as  there  are  along 
the  Sangamon  river  have  been  derived  chiefly  from  the  materials  washed 
out  from  between  the  Kansan  and  lllinoian  till.  They  are  useful  for 
abrasives  and  as  constituents  of  mortar  and  cements.  The  best  sand- 
stone in  the  county  for  building  material,  No.  20,  in  the  typical  section 
given  above,  outcrops  at  Koke's  Mill,  where  layers  from  six  inches 
to  two  feet  in  thickness  and  of  fair  crushing  strength  can  be  obtained. 
This  is  the  material  which  was  used  in  the  construction  of  St.  Paul's 
Episcopal  Church  in  Springfield  in  1848.  The  stone  is  not  very  firm 
and  weathers  to  a  brown  color  by  the  oxidation  of  the  iron  which  it 
contains. 

A  better  building  stone  is  furnished  by  limestone  (Fig.  9)  the  stone 
obtained  from  the  majority  of  the  eight  quarries  indicated  on  the  accom- 


FIG.  9 — Outcrop  of  the  limestone  (No.  8  in  typical  section)  which  furnished  the 
stone  for  the  Old  State  House,  Springfield.  Quarry  a  quarter  of  a  mile  west  of 
Crow's  Mill. 


GEOLOGY    OE    SANGAMON    COUNTY 


i; 


panying  map.  As  will  be  noted  it  is  exposed  in  various  creek  beds  and 
is  widely  spread  over  the  county.  This  is  the  material  which  was- 
employed  in  the  construction  of  the  old  State  House  erected  at  Spring- 
field between  1837  and  1853,  at  a  cost  of  $260,000.00.  This  building- 
is  now  used  as  the  county  building.  The  chief  quarry  for  the  stone, 
No.  8,  in  the  typical  rock  section  given  above,  was  at  Crow's  Mill  eight 
miles  south  of  the  public  square  in  Springfield.  The  place  which  at  that 
time  was  a  rocky  quarry,  has  been  smoothed  out  by  the  hand  of  time 
so  that  now  a  visitor  at  that  place  sees  scarcely  a  trace  of  the  former 
excavations,  a  green  carpet  of  grass  and  clover  having  been  spread  as  a 
mantle  over  the  old  quarry.  (Fig.  10.)  The  present  State  House  is 
constructed  of  Niagara  limestone  obtained  from  the  quarries  of  Joliet 


FIG.  10 — Old  Crow's  Mill  quarry,  now  overgrown  with  grass. 

and  Lemont.  Since  the  Crow's  Mill  limestone  soon  turns  to  an  unat- 
tractive brown  shade,  it  is  not  very  much  prized  in  building.  How- 
ever, it  is  abundant  enough  in  quantity  to  furnish  a  valuable  stone  of 
medium  grade  which  can  be  used  to  advantage  in  the  construction  of 
foundations,  in  bridge  building  and  in  the  manufacture  of  quicklime. 

CLAY  DEPOSITS. 

Much  more  valuable  as  a  building  material  than  the  products  of  any 
of  the  quarries  is  the  output  of  the  clay  pits.  In  quantity  clay  is  prac- 
tically unlimited.  The  manufacture  of  brick,  tile  and  earthen  ware, 


18  GEOLOGY   OF   SAXGAMOX    COUNTY 

though  in  its  infancy  yields  annually  considerable  sums.  For  example, 
in  this  county  in  1906  drain-pipe  to  tho  value  of  $10,194.00  and  brick 
to  the  value  of  $208,732.00  were  produced.  There  are  thirteen  com- 
panies engaged  in  this  industry.  The  material  which  they  employ  is 
obtained  from  either  the  yellow  loess-like  clay,  six  to  eight  feet  in  thick- 
ness; the  weathered  clay,  six  feet  thick,  underlying;  or  the  blue  compact 
clay,  forty-five  feet  thick  which  is  below  that.  All  of  these  materials 
produce  brick  of  average  strength  and  about  2.66  in  specific  gravity. 
A  typical  analysis  of  the  composition  of  the  clays  used  in  the  manu- 
facture of  brick  at  a  Springfield  clay  pit  is  as  follows : 

Si(X        =60.31     Alo08      =17.74     C  =    6.71 

Fe,63       =    5.04     K,0          =    2.88     MgO  1.96 

FeO       =    1.96     XaoO  1.07     TiCX     =      .84 

H20      =      .81     CaO  .41     S  .14 

COAL  DEPOSITS. 

The  clay,  sand,  limestone  and  sandstone  are  far  surpassed  in  value  by 
the  coal  mined  in  the  county.  Forty-one  mines,  thirty-seven  of  them 
producing,  are  located  on  the  accompanying  map.  (Fig.  11.)  Their 
output  in  1906  gave  Sangamon  county  the  leading  place  as  coal  pro- 
ducer in  the  State  of  Illinois,  and  since  that  time  its  premiership  has 
been  contested  by  Williamson  county  alone.  In  the  25  years  before 
1907  Sangamon  had  lead  all  counties  in  the  State  in  coal  production, 
having  yielded  more  than  fifty-two  million  tons.  In  1908,  6,553  men 
working  in  these  mines  produced  about  five  million  tons  of  coal,  which 
cost  the  consumer  something  more  than  ten  million  dollars.  Xo  other 
single  source  of  wealth  contributed  so  much  to  the  prosperity  of  the 
people  in  this  county.  In  his  work  on  the  geology  of  the  State,  in  the 
sixties,  Worthen  numbered  the  different  coal  beds  of  the  State  from 
1  to  17,  No.  1  being  considered  the  lowest  and  oldest  geologically  and 
the  others  supposed  to  follow  in  order.  The  chief  beds  of  the  county 
lie  about  one  hundred  and  sixty  feet  belowT  coal  Xo.  8,  which  as  pointed 
out  in  the  typical  section  above  is  about  one  hundred  feet  below  the 
surface  deposits;  in  other  words  the  chief  coal  deposits  are  from  two 
hundred  to  three  hundred  fifty  feet  below  the  surface,  while  south  of 
Sangamon,  for  example,  at  Mt,  Olive,  in  Macoupin  county  they  are  four 
hundred  twenty-five  feet,  and  in  the  count v  eat.  Macon,  at  Decatur, 
they  are  six  hundred  feet  deep,  due  to  the  prevailing  clip  of  the  strata 
to  the  south  and  east. 

The  two  beds,  Xos.  5  and  6,  are  readily  distinguished  by  their  phy- 
sical characteristics.  Xo.  5  is  known  as  Horseback  coal,  because  of  clay 
fissures  or  horsebacks  due  to  vertical  partings,  filled  with  clay  when  the 
fissures  are  wide  or  with  shaly  calcareou?  deposits  when  narrow.  The 
bed  is  six  feet  thick,  has  a  good  roof  and  furnishes  a  large  output.  Bed 
Xo.  6  is  called  Blueband  coal  since  about  two  feet  from  the  bottom  of 
the  bed  there  is  a  horizontal  band  of  slaty  material  from  one  inch  to  an 
inch  and  a  half  in  thickness.  The  separation  in  this  coal  is  along 
horizontal  rather  than  vertical  lines.  The  bed  is  from  six  to  eight  feet 


GEOLOGY    OF    SANGAMOX    COUNTY 


19 


20  GEOLOGY    OF    SAXGAMOX    COUNTY 

thick.  Composition  and  ash  content  of  Xos.  5  and  6  are  quite  similar, 
though  Xo.  6  contains  a  slightly  larger  amount  of  moisture,  and  it  is 
said  that  Xo.  6  affords  the  largest  amount  of  heat  for  a  given  sum 
of  money. 

Two  higher  coals,  too  thin  for  use  at  present,  lie  fifty  and  one  hun- 
dred sixty  feet,  respectively,  above  Xo.  5.  Several  beds  have  been  found 
below  Xo.  5.  At  Riverton  a  diamond  drill  showed  two  seams  each  about 
two  and  a  half  feet  thick  lying  respectively  one  hundred  twenty-five 
feet  and  two  hundred  fifty  feet  below  Xo.  5,  and  a  four  foot  bed  at 
three  hundred  twenty  feet  below  Xo.  5. 

In  the  drill  at  Divernon  the  first  coal  encountered  was  a  nine-inch 
seam  at  a  depth  of  one  hundred  fifty-one  feet  below  the  surface.  This 
is  probably  coal  Xo.  8  which  outcrops  at  Eiverton.  At  a  depth  of  two 
hundred  sixty-one  feet,  a  two  inch  seam  was  met,  and  at  three  hundred 
twenty  feet  the  best  coal  bed  of  the  county,  Xo.  6,  was  discovered.  It 
is  seven  feet  eleven  inches  in  thickness.  Xot  satisfied  with  this  bonanza 
the  drillers  proceeded  farther  with  the  following  result:  At  three  hun- 
dred sixty-nine  feet  they  found  a  bed  about  three  feet  thick :  at  three 
hundred  eighty  feet  one  one  foot  thick;  at  four  hundred  thirty  feet 
one  two  feet  thick:  at  four  hundred  sixty,  one  one  foot  one  inch  thick; 
at  four  hundred  ninety,  one  a  foot  and  two  inches  thick;  at  five  hun- 
dred fourteen,  one  a  foot  and  eight  inches;  at  five  hundred  fifty-nine 
feet,  one  four  feet  five  inches  thick.  This  was  the  last  bed  found  and 
at  six  hundred  four  feet  the  boring  was  discontinued  since  a  conglom- 
erate was  reached  which  was  thought  to  be  a  part  of  the  Mansfield 
formation.  Though  a  line  of  demarcation  between  the  McLeansboro 
and  the  Carbondale  is  difficult  to  locate  in  this  boring,  or  at  any  place 
in  the  county,  it  may  possibly  be  found  at  about  two  hundred  seventy- 
five  feet  beloAv  the  surface. 

Coal  is  the  most  valuable  product  of  the  county  and  but  few  counties 
in  any  state  in  the  Fnited  States  even  in  those  regions  reputed  for  their 
mineral  wealth,  derive  more  valuable  or  useful  mineral  substances  than 
this  which  is  obtained  right  here  in  Sangamon.  AVithout  these  coal 
seams  in  this  or  other  regions,  there  could  be  no  manufacturing  on  a 
large  scale,  no  railroads,  no  cities. 

The  following  represents  a  typical  analysis  of  Sangamon  county  coal : 
Moisture,  10.5  per  cent;  Ash,  7.7  per  cent;  Volatile  material,  38.9  per 
cent ;  Fixed  carbon,  42.9  per  cent.  The  pure  coal  amounts  to  74.25  per 
cent  and  the  sulphur,  3.5  per  cent.* 

Physically  the  coal  is  sometimes  shaly  but  usually  compact  and  breaks 
with  conchoidal  fracture;  its  hardness  is  2.5;  its  specific  gravity  1.4.  In 
color  it  is  black.  The  color  of  its  powder  is  brown.  In  luster  it  is 
earthy  to  vitreous.  It  dissolves  in  potassium  hydrate  without  coloring  the 
solution  brown  as  does  lignite  or  other  less  completely  mineralized  hydro- 
carbon compounds.  "When  bleached  in  nitric  acid  and  potassium  chlor- 
ate and  washed  in  alcohol,  its  vegetable  texture  can  be  plainly  seen  and 
this  is  one  means  of  knowing  that  coal  has  been  made  from  vegetation. 
Another  means  of  establishing  this  fact  is  that  coal  can  be  actually  made 


*  Illinois  State  Geological  Survey,  Bulletin  No.  3, 1906,  p.  73. 


GEOLOGY   OF    SANGAMON    COUNTY 


21 


in  the  laboratory  by  heating  wood  in  a  test  tube.  First  a  white  cloud 
of  steam  is  driven  off.  Then  oxygen  and  hydrogen  are  separated  leaving 
lignite.  Next  when  the  tube  is  closed  to  keep  the  oxygen  of  the  air  from 
uniting  with  the  carbon.,  carburreted  hydrogen  is  formed  after  continued 
heating.  This  gas  explodes  the  weakest  part  of  the  tube  and  is  burnt  off. 
As  the  heating  is  continued  tar  is  formed,  then  bituminous  coal  and 
finally  anthracite.  A  third  reason  for  the  belief  is  that  coal  is  now 
being  slowly  formed  where  wood,  buried  and  protected  from  oxidation, 
is  losing  its  less  stable  constituents,  as  for  example  in  peat  swamps  and 
in  abandoned  mines.  The  timbers  in  an  abandoned  mine  in  the  Hartz 
mountains  which  had  stood  under  water  for  five  hundred  years,  upon  the 
draining  of  the  mine  recently,  were  found  to  have  been  changed  to  lig- 
nite. Again  in  many  mines  tree  stumps  are  still  in  position.  And 
finally  more  than  seven  hundred  species  of  plants  have  been  found  and 
determined  in  coal.  It  is  thus  evident  that  the  materials  which  furnish 
the  coal  are  vegetable,  but  the  manner  of  their  accumulation  is  not  so 
clear.  When  exposed  to  the  air  wood  rapidly  oxidizes,  but  when  pro- 
tected under  water  conditions  are  favorable  for  gradual  loss  of  volatile 
material  with  retention  of  fixed  carbon.  Peat  swamps  furnish  favorable 
surroundings  for  coal  formation.  Materials  carried  to  them  by  floods 
are  protected  from  oxidation.  Vegetation  grows  on  the  bottom,  on  the 
top  and  throughout  the  mass  of  algae,  mosses  and  other  low  vegetable 
forms.  The  swamp  being  buried  under  clay  and  sand  and  depressed 
by'  change  of  level  of  supporting  strata,  is  compressed  by  the  great 


FIG.   12 — Sangamon  county  is  a  prairie,  save  where  streams  have  fashioned  valleys 
or  glaciers  deposited   their  burdens. 


22  GEOLOGY   OF    SANGAMOX    COUNTY 

accumulation  of  material.  Alternate  rising  and  sinking  of  the  land  may 
occasion  a  repetition  of  these  processes,  until  several  layers  of  coaly 
material  are  formed.  Subsequent  deep  burial,  great  pressure  and  final 
elevations  produce  a  coal  field  with  various  layers.  The  cross  sections  of 
the  coal  fields  in  Sangamon  county  show  that  such  must  have  been  the 
history  of  the  formation  of  our  coal. 

SOILS. 

Fully  as  important  as  the  various  rock  strata,  clay  pits  and  coal  de- 
posits for  the  prosperity  of  Sangamon  county,  is  the  nature  of  the  sur- 
face soil.  (Fig.  12.)  Though  but  a  foot  or  two  in  thickness,  the  soil 
is  the  source  of  millions  of  dollars  worth  of  food  and  raiment.  In  1909 
the  agricultural  products  of  the  county  exceeded  nine  millions  of  dollars 
in  value.  Such  an  enormous  yield  would  be  impossible  under  less  favor- 
able conditions.  There  are  four  chief  kinds  of  soil;  the  Marshall  silt 
loam,  the  Miami  silt  loam,  the  Miami  black  clay  loam  and  the  Kaskaskia 
loam,  named  in  order  of  their  abundance.  These  may  be  recognized  by 
one  riding  through  the  county,  in  the  early  spring  largely  by  their  color 
as  well  as  by  their  texture  and  their  position  in  relation  to  slopes  and 
levels. 

Miami  silt  loam  occupies  about  seventeen  per  cent  of  the  area  of  the 
county.  It  is  a  granular  soil  crumbling  readily;  in  color  it  is  brown, 
but  nearly  black  when  wet.  The  color  is  due  to  the  large  amount  of 
vegetable  matter  which  it  contains.  It  extends  to  a  depth  of  about 
eighteen  inches.  It  occupies  broad  rather  level  areas,  usually  avoiding 
bluffs,  but  found  on  remnants  of  the  old  moraines  in  Buffalo  Hart  and 
Mechanicsburg  townships.  It  is  a  loess,  weathered  and  containing  a 
large  per  cent  of  humus.  Corn,  oats  and  hay  thrive  on  this  soil. 

Miami  silt  loam  occupies  about  seventeen  per  cent  o  f the  area  of  the 
county  ;it  is  looser,  more  floury  and  porous,  lighter  in  color  and  contains 
less  organic  material.  It  is  rarely  more  than  twelve  inches  in  depth,  and 
is  found  along  the  slopes  of  the  Sangamon  river  and  its  tributaries,  being 
characteristic  of  hilly  country  with  broken  topography  and  good  drain- 
age. Fruit,  grass  and  wheat  thrive  on  it. 

Miami  black  clay  loam  constitutes  sixteen  per  cent  of  the  area  of  the 
county.  It  is  darker  than  the  Marshall  soil,  heavy,  sticky  so  as  to  merit 
the  name  of  "Gumbo,"  granulated  and  subject  to  extensive  cracking 
when  baked  in  the  hot  summer  sun.  Driving  along  country  roads  after  a 
rain  storm,  one  readily  recognizes  this  soil  since  it  dries  less  readily  is 
sticky  and  subject  to  ruts.  Its  depth  is  about  eighteen  inches.  It  oc- 
cupies level  areas,  is  subject  to  swamps  because  of  its  poor  drainage,  con- 
tains a  large  amount  of  organic  matter,  washed  in  from  surrounding 
lands  or  derived  from  the  imperfect  oxidation  of  local  vegetation.  This 
organic  matter  devaying  forms  acids  which  attack  the  silt  particles  and 
renders  the  soil  more  sticky.  The  Miami  black  clay  loam  is  the  typical 
black  prairie  soil  which  has  made  Illinois  famous  for  its  corn  produc- 
tion. No  soil  makes  better  corn  land. 

If  there  were  no  swamps  there  would  be  no  Miami  black  clay  loam. 
If  there  were  no  active  erosion  there  would  be  no  Miami  silt  loam  and 


GEOLOGY    OF    SANGAMON    COUNTY  ^ 

(.lie  only  soil  in  the  county  would  be  that  known  as  the  Marshall  silt 
loam  or  the  following: 

The  Kaskaskia  loam  is  a  somewhat  sandy,  silty,  granular,  brown  to 
drab  soil,  reaching  to  a  depth  of  about  fourteen  inches  and  found  most 
extensively  on  the  bottom  lands,  approximately  about  ten  feet  above  the 
river,  along  the  Sangamon  and  its  tributaries.  It  is  an  alluvial  soil, 
generally  valuable  if  not  flooded,  for  corn,  oats,  hay  and  especially  for 
pasture  and  timber. 

WATER. 

In  water  resources,  Sangamon  county  is  fortunate.  On  account  of  the 
low  topographic  relief  (Fig.  12)  which  in  the  maximum  does  not  exceed 
two  hundred  feet,  and  on  account  of  the  earth  cover  of  the  comparatively 
level  strata,  the  water  line  is  at  a  comparatively  uniform  level.  The 
Sangamon  and  its  tributaries  flow  in  a  generally  northwest  direction. 
These  streams  furnish  water  for  the  towns  and  cities,  but  throughout 
the  county,  wells  furnish  the  main  supply  of  water.  More  than  fifty  per 
cent  of  the  wells  are  sunk  as  deep  as  the  top  of  the  Illinoian  till  and  find 
an  abundant  supply  of  water  at  an  average  depth  of  twenty-one  feet. 
Fourteen  per  cent  of  the  wells  are  sunk  as  far  as  the  top  of  the  Kansas 
till.  That  is  they  have  penetrated  the  sand,  loess  and  Illinoian  till  and 
have  an  average  depth  of  thirty-five  feet.  Seventeen  per  cent  have  been 
so  sunk  as  to  avoid  a  portion  of  the  loose  surface  deposits  and  have 
penetrated  as  far  as  bed  rock  with  an  average  depth  of  twenty-seven 
feet.  On  the  whole  since  the  water  in  these  wells  has  been  strained 
through  soil  and  sand,  it  is  wholesome  where  not  contaminated  by  man. 
But  a  small  amount  of  mineral  matter  is  contained  in  this  water.  The 
salts  found  are  of  the  most  part  calcium  and  magnesian  carbonate  and 
a  small  amount  of  iron  oxydes  and  some  sulphates.  None  of  these  are 
present  in  quantities  sufficiently  great  to  render  it  less  valuable  for  drink- 
ing purposes  or  for  use  in  steam  boilers. 

CONCLUSION. 

Sangamon  county  is  a  synonym  for  a  country  of  plains,  the  highest 
point  in  the  county,  in  the  southwest,  bein^  seven  hundred  twenty  feet 
above  sea  level,  the  highest  rock  strata  being  seven  hundred  seventeen 
feet.  The  lowest  point  in  the  county,  being  also  the  lowest  rock  surface, 
is  four  hundred  and  ninety  feet,  in  the  southwest  corner  where  the  San- 
gamon leaves  the  county.  Such  a  level  surface  shows  slight  disturbance 
of  original  rock  strata  either  by  the  pressure  of  the  forces  contracting 
the  earth,  or  by  the  erosion  of  rapidly  flowing  rivers.  The  surface  is 
even  more  level  than  it  otherwise  would  have  been  had  it  not  been 
smoothened  out  by  the  materials  brought  down  from  northern  regions 
by  the  glaciers  and  scattered  here  and  there  both  by  wind  and  by  water. 
Glaciers  have  done  their  best  to  spread  the  blanket  of  oblivion  over  the 
ideological  past  of  the  county.  But  ours  if  the  advantage  which  comes 
from  that  past. 

The  slow  process  of  millions  of  years  have  contributed  to  our  pros- 
perity. As  we  consider  the  enormous  supplies  of  coal,  the  boundless 


24  GEOLOGY    GV   SANGAMON    COUNTY 

deposits  of  stone  and  clay,  the  marvelously  fertile  soil  and  the  wholesome 
and  abundant  water,  we  realize  that  all  the  periods  of  the  geological 
history  with  its  bundle  of  processes  have  given  to  the  inhabitants  of 
Sangamon  county  a  region  well  qualified  to  be  one  of  the  garden  spots 
of  America. 

LITERATURE  OX  SAXGAMOX  COUNTY  GEOLOGY. 

Bain,  H.  F. — Illinois  State  Geological  Survey,  Bulletins  No.  1  to  Xo. 

15   (1906-1910.) 

Do  Wolf,  Frank — Illinois  State  Geological  Survey.,  Bulletin  Xos.  1G,  17. 
Leverett,  Frank — I".  S.  Geological  Survey,  17th  Annual  Report.  Part 

II,  pp.  701-842. 
Report  of  Illinois  Board  of  World's  Fair  Commissioners,  1893,  pp. 

77-92, 

Whitnev,   Milton — Report  of  Illinois  Board  of   World's  Fair  Commis- 
sioners, 1893,  pp.  93-111. 
U.  S.  Dept.  of  Agriculture — Soil  Survey  of  Sangamon  County,  1903, 

pp.  1-21. 
Worthen,  A.  H.— Geological  Survey  of  Illinois  Chiefly.     Vol.  V,  1873, 

pp.  306-319. 
Economical  Geology  of  Illinois.     Vol.  Ill,  1882,  pp.  322-336. 


Makers 
Syracuse,  N.  Y. 

PAT.  JAN  21,  1908 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


